New wood tech­nol­ogy may of­fer hope for strug­gling tim­ber

Kuwait Times - - TECHNOLOGY -


John Red­field watches with pride as his son moves a laser-guided pre­ci­sion saw the size of a semi-truck wheel into place over a mas­sive panel of wood. Red­field’s fin­gers are scarred from a life­time of cut­ting wood and now, af­ter decades of de­cline in the log­ging busi­ness, he has new hope that his son, too, can make a ca­reer shap­ing the tim­ber felled in south­ern Ore­gon’s forests. That’s be­cause Red­field and his son work at D.R. John­son Lum­ber Co, one of two US tim­ber mills mak­ing a new wood prod­uct that’s the buzz of the con­struc­tion in­dus­try. It’s called cross-lam­i­nated tim­ber, or CLT, and it’s made like it sounds: rafts of 2-by-4 beams aligned in per­pen­dic­u­lar lay­ers, then glued - or lam­i­nated - to­gether like a giant sand­wich.

The re­sult­ing pan­els are lighter and less en­ergy-in­ten­sive than con­crete and steel and much faster to as­sem­ble on-site than reg­u­lar tim­ber, pro­po­nents say. Be­cause the grain in each layer is at a right an­gle to the one be­low and above it, there’s a counter-ten­sion built into the pan­els that sup­port­ers say makes them strong enough to build even the tallest sky­scrapers. “We be­lieve that two to five years out, down the road, we could be see­ing this grow from just 20 per­cent of our busi­ness to po­ten­tially 60 per­cent of our busi­ness,” said Red­field, D.R. John­son’s chief op­er­at­ing of­fi­cer. “We’re see­ing some ma­jor growth fac­tors.” From Maine to Arkansas to the Pa­cific North­west, the ma­te­rial is spark­ing in­ter­est among ar­chi­tects, en­gi­neers and re­searchers. Many say it could in­fuse strug­gling for­est com­mu­ni­ties like Rid­dle with new eco­nomic growth while re­duc­ing the car­bon foot­print of ur­ban con­struc­tion with a re­new­able build­ing ma­te­rial.

Lo­cal tree species

Vis­ually blem­ished wood that cur­rently goes to waste can be used in the mid­dle lay­ers of a CLT panel with­out sac­ri­fic­ing strength or look. Sup­port­ers say it could bring sawmills back on­line while im­prov­ing for­est health through thin­ning dense stands and mak­ing use of low-value wood and lo­cal tree species. Trees as small as 5 inches in di­am­e­ter at the top and those dam­aged by pests and wild­fire are prime can­di­dates.

But chal­lenges re­main be­fore CLT be­comes as com­mon in the United States as it is in Europe and Canada, and not all builders are sold. US build­ing codes gen­er­ally place height limits on all-wood build­ings for safety rea­sons, though a spe­cial com­mit­tee of the In­ter­na­tional Code Coun­cil is in­ves­ti­gat­ing po­ten­tial changes to ad­dress the use of CLT in such struc­tures. And re­search is still un­der­way on crit­i­cal ques­tions of how these build­ings with­stand fire and earth­quakes in high­seis­mic re­gions. Build­ing codes in Ore­gon al­low cut­ting-edge de­signs us­ing new tech­nol­ogy like CLT in some cases, but only af­ter rig­or­ous test­ing and an in­ten­sive ap­proval process. That can make such projects cost-pro­hib­i­tive, said Peter Du­sicka, an en­gi­neer­ing pro­fes­sor at Port­land State Univer­sity who’s been re­search­ing the strength of CLT pan­els. “The early adopters are look­ing at it and see­ing it as a good op­por­tu­nity,” but be­fore CLT can take off, there will have to be more ex­am­ples to get peo­ple ex­cited and more mills pro­duc­ing it, said Thomas DeLuca, pro­fes­sor and di­rec­tor of Univer­sity of Wash­ing­ton’s School of En­vi­ron­men­tal and For­est Sciences.

SmartLam in Mon­tana is the other com­pany pro­duc­ing CLT pan­els. This spring, cross-lam­i­nated tim­ber will get its ul­ti­mate test in the United States when a Port­land ar­chi­tec­tural firm breaks ground on a 12-story wood build­ing in the city’s trendy Pearl Dis­trict. It would be the tallest all-wood build­ing in the world con­structed in a seis­mic zone and the tallest all-wood build­ing in North Amer­ica. An all-wood build­ing in Nor­way is taller, but is not in a seis­mic zone. An 18-story wood build­ing in Bri­tish Columbia is also taller, but rests on a tra­di­tional con­crete core.

Re­silient de­sign

Lever Ar­chi­tec­ture is us­ing $1.5 mil­lion it won in a tall wood build­ing com­pe­ti­tion spon­sored by the US De­part­ment of Agri­cul­ture and the soft­wood in­dus­try that’s in­tended to pro­mote CLT as a do­mes­tic build­ing ma­te­rial. A 10-story res­i­den­tial tower in New York City also got $1.5 mil­lion. The Port­land firm has been work­ing with sci­en­tists at Port­land State Univer­sity and Ore­gon State Univer­sity to test the pan­els’ strength by sub­ject­ing them to hun­dreds of thou­sands of pounds of pres­sure. They are also test­ing var­i­ous meth­ods for join­ing the mas­sive pan­els to­gether.

“We’re look­ing at cre­at­ing a re­silient de­sign, a de­sign that could with­stand a ma­jor earth­quake - ba­si­cally the earth­quake that we all worry about - and be re­paired,” said Thomas Robin­son, founder of Lever Ar­chi­tec­ture. The re­sults of the struc­tural test­ing in Ore­gon will be made pub­lic for other US de­sign­ers, bring­ing the ma­te­rial one step closer to the main­stream, Du­sicka said. Back in Rid­dle, a tiny town tucked in the mist-shrouded forests of Dou­glas County, Red­field is once more ex­cited about tim­ber in a place where log­ging used to be king. The 125-em­ployee com­pany has been in­un­dated with vis­i­tors from around coun­try in­ter­ested in tour­ing their new CLT busi­ness ex­pan­sion. Watch­ing as lay­ers of beams whirred through a glue ma­chine, Red­field said: “We’re able to take wood that may be turned into chips or pulp and turn it into a prod­uct that’s pretty ex­cit­ing.”—AP

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